U.S. Pat. No. 3,663,667 discloses a process for producing multimetal alloy powders. Thus, multimetal alloy powders are produced by a process wherein an aqueous solution of at least two thermally reducible metallic compounds and water is formed, the solution is atomized into droplets having a droplet size below about 150 microns in a chamber that contains a heated gas whereby discrete solid particles are formed and the particles are thereafter heated in a reducing atmosphere and at temperatures from those sufficient to reduce said metallic compounds to temperatures below the melting point of any of the metals in said alloy.
U.S. Pat. No. 3,909,241 relates to free flowing powders which are produced by feeding agglomerates through a high temperature plasma reactor to cause at least partial melting of the particles and collecting the particles in a cooling chamber containing a protective gaseous atmosphere where the particles are solidified. In this patent the powders are used for plasma coating and the agglomerated raw materials are produced from slurries of metal powders and binders. Both the U.S. Pat. No. 3,663,667 and the U.S. Pat. No. 3,909,241 patents are assigned to the same assignee as the present invention.
In European Patent Application No. WO8402864 published Aug. 2, 1984, also assigned to the assignee of this invention, there is disclosed a process for making ultra-fine powder by directing a stream of molten droplets at a repellent surface whereby the droplets are broken up and repelled and thereafter solidified as described therein. While there is a tendency for spherical particles to be formed after rebounding, it is stated that the molten portion may form elliptical shaped or elongated particles with rounded ends.
Low melting temperature metal powders were heretofore produced by gas or water atomization or precipitation from solution. "Low melting temperature" metal as used herein are metals having a melting or liquidus temperature at or below about 430.degree. C. and include elements such as lead, indium, zinc and tin and alloys thereof having such melting or liquidus temperatures. By a "low melting temperature" metal based material as used herein means that the foregoing low melting temperature materials constitute the major portion of the material thus include the lower melting temperature metal per se as well as allows in which the lower melting temperature metal is the major constituent, normally about 50% by weight of the alloy but in any event the low melting temperature metal or metals are the constituent or constituents having the largest percentage by weight of the total alloy. Such metals and alloys have a wide range of industrial applications such as precision solders which are that class of materials that melt below about 430.degree. C. or 800.degree. F. Gas atomization produces fine metal alloy powder often with a fairly wide particle size distribution. Water atomization, while more more cost effective than gas atomization produces a nonspherical powder particle which is often higher in oxygen than its gas atomized counterpart. Precipitation offers the potential for a high yield of fine powder, yet nonspherical powder morphology and potential organic contamination are potential short comings of the hydrometallurgical processes heretofore used.
It is believed therefore that a relatively simple process which enables finely divided metal alloy powders to be hydrometallurgically produced from sources of the individual metals is an advancement in the art.